How to Dig Up & Store Dahlia Tubers Overwinter

Once Dahlia leaves are blackened by the frost, it’s a common practice to dig them up and prepare for storage over the winter

How to Lift Dahlia Tubers from the Soil

To lift Dahlia tubers before storing them overwinter, you need a garden fork, some pots or crates for storage in a cool, dry place, and something to cover them with: vermiculite, sand, sawdust, or dry compost are all great for storing tubers.

TRANSCRIPT
We’ve had a hard frost last night. So, just checking the dahlias in the garden and some of them have been nipped by frost. You’ll see that where the leaves start going black, they go black and they wilt. So now it’s probably a better time to get them dug up and prepared for storage over the winter.
The reason why we dig dahlias up: the species originated from Mexico, so they’re not fantastically hardy. The best thing to do is just find out which one you want to dig up. Put your fork in. Nice and gently. Try not to put it too close to the stem. I’ve gone about six inches away from the stem. Give it a quick tug, and you’ll hear it just kind of give way, so grab it by the stem, and give it a good shake, and you’ve got a good dahlia tuber. Try and get rid of some of this soil, put it back on the garden, and then we’ll cut the stems off. You might even get some of that, which is a new plant. Just cut the stems off the original plant. Don’t have to cut them right the way down to the ground, something like that. And just keep on taking a bit of soil off, don’t take all of it off. And that’s it. Once we get back to the nursery, we’ll give it a proper tidy off. Make sure it’s all alright. And then we’ll get it prepared for winter.
Right, so we’ve dug our dahlia tuber up, take all the old soil off.
Main reason is just to kind of check the condition of the tubers. And that looks really good. So the tubers, if you’re not sure, they should be as firm as a potato. So, if they’re a bit squishy and soft, take them off. And then the stems usually like that for a week or so, just to let all the water drain out of these old stems, so it’s completely dry.
And then once it’s all dried out, we could either use a crate or a big black pot. So, at the moment, we’re just going to use a big black pot, and I’m going to use vermiculite. Put your dahlia tuber in and just fill it up. So we put the dahlia tuber in the pot, covered up. You don’t need to cover it right up to the top, just as long as you cover the main part of the tuber. And then these can either go into a dry frost-free shed under the bench of a green house, or in a cold conservatory, just put them underneath the bench or something. And in the spring, once it starts to warm up a bit, or if you want to force them, you either bring them back into the greenhouse, start watering them gently.
That’s ready for winter. If you’ve got a lot of them, probably best off in black crates, such as that. So, you just put them in, make sure they’re labelled, put a white label on, tie them to the end of the stem. Put a bit of vermiculite in the bottom and then put them on the top. If you haven’t got vermiculite, you can use dry compost, sand, sawdust.
What I usually do if I’ve got a lot of dahlia tubers, and they’re in crates, I’ll stack them on top of each other and then cover everything with fleece, and they’ll be asleep for winter.

When Should I lift my Dahlia Tubers for Winter?

It is best practice, recommended by the National Dahlia Society to let the first or second frost blacken the dahlia stems, so that they wither and die back, which gives the tubers as much time as possible to store energy.
In most parts of the UK, this means early November; in colder Northern regions it may be late October.

But if you are going away before the first frost, lift them as late as possible and they should be fine.

Do I Really Need to Dig up Dahlia Tubers for Winter? It Depends!

Dahlia tubers in the UK usually survive outdoors overwinter, especially in sandy, free draining soils that have no waterlogging in Winter.

If you leave them in the soil, protect them with thick mulch, ideally something dry like straw or woodchips, rather than compost or manure, which hold more moisture.
As a rule of thumb, each degree below zero penetrates one inch of soil, therefore 4-5 inches of mulch should be plenty in most parts of the UK.

Many gardeners do both: dig up some tubers, and leave some in the ground under mulch.

Can I Leave Potted Dahlias in Their Pots Over Winter?

Yes, you can leave dahlias in their pots over winter in a frost free place, and put them outside again when the last frost has passed.

As with dahlias in the soil, it’s best to wait until the leaves are blackened by frost, or mid-November if they are growing in a frost free place.